The research, led by Martin Béland of Laval University’s Digital Forest Lab together with Gordon Bonan of the NSF National Center for Atmospheric Research, Hideki Kobayashi of the Japan Agency for Marine-Earth Science and Technology, and Dennis Baldocchi of the University of California, Berkeley, tackles a stubborn blind spot in radiative transfer modeling. Computer models that simulate forest canopy microclimates, from the air temperature at the forest floor to the fluxes that link land surfaces to the global atmosphere, all begin with the same calculation: how much solar radiation does the canopy reflect, and where does the rest go? Classic one-dimensional schemes such as the Norman model from 1979 and the two-stream formulations of Dickinson and Sellers divide that absorbed energy among sunlit leaves, shaded leaves, and soil. Wood simply does not appear in the ledger.

Yet recent work has shown that woody structures absorb a significant fraction of incoming near-infrared radiation in dense forests and store it as heat. Because stems are massive, they warm slowly through the day and release that stored heat at night, shifting the diurnal rhythm of air temperature inside the canopy. That matters for the organisms living in the understory and on the forest floor, for the closure of energy budgets at eddy covariance flux towers, and for land surface models such as the Community Land Model, which currently lumps leaves and stems together into a single plant area index with weighted optical properties, never resolving their separate absorption.

The challenge is structural. Stems and branches are wildly heterogeneous in size, orientation, and density, and their exposure to sunlight depends on where they sit within the canopy. The team’s solution was to modify the radiative transfer component of the CanVeg2 multilayer canopy model, which uses the Norman scheme, so that wood is explicitly represented. The mathematics is elegant: the projected areas of leaves and stems are combined in the Beer-Lambert extinction equation, and each canopy layer’s intercepted radiation is partitioned between leaves and wood in proportion to their projected areas in that direction, with leaf area index and wood silhouette area index weighted by their respective projection factors and clumping indices. The full system is solved as a tridiagonal set of equations, keeping the model fast enough for routine microclimate simulation.

One subtlety the researchers had to confront is that stems, like leaves, are not randomly distributed in space, and this clumping affects how much radiation they intercept. With no modern data available, the team mined a remarkable historical dataset: light transmission measurements collected in the 1980s by a tram system shuttling PAR sensors back and forth through a temperate deciduous forest near Oak Ridge, Tennessee, during leaf-off conditions in January 1981. Inverting Beer’s law against those measurements, and correcting for the fact that bark scatters more light than leaves and thus inflates ground-level transmission, the team arrived at a wood clumping index of 0.75 for a temperate deciduous forest. Sensitivity tests showed this parameter matters: shifting it from 0.75 to 0.6 or 0.9 changed the radiation absorbed by stems by roughly 16 percent in both directions, even though canopy albedo barely moved.

Validating a one-dimensional model requires a trustworthy benchmark, and here the team turned to ground-based lidar and three-dimensional ray tracing. At four broadleaf deciduous sites spanning a structural gradient, Harvard Forest in Massachusetts, Morgan-Monroe State Forest in Indiana, the Smithsonian Environmental Research Center in Maryland, and the Pasoh Forest Reserve in Malaysia, each plot was scanned from 121 lidar positions to build dense 3D voxel grids, 30 centimeters on a side, that separately map leaf area density and wood silhouette area density. These voxel maps fed the FLiESvox ray tracing model, which tracks photons through the full three-dimensional canopy, including multiple scattering within clumped foliage using the recollision probability theory of Smolander and Stenberg. Running FLiESvox was computationally demanding: covering varying sun angles and diffuse fractions required 81 simulations in the PAR waveband and 81 in the near-infrared.

The agreement between the modified one-dimensional model and the 3D benchmark was strikingly good. Across all four sites, root mean square errors between vertically integrated absorbed fluxes came to about 12 watts per square meter in the PAR and about 8 watts per square meter in the near-infrared. Vertical profiles of absorption by sunlit leaves, shaded leaves, and wood agreed with mean errors per layer of a few tenths of a watt per square meter. A leaf-off test case, where only wood remains in the canopy, also showed strong agreement between the two models, suggesting the approach works year-round. The step-by-step model comparisons revealed why each modification mattered: adding foliage clumping lowered albedo and let light penetrate deeper, adding wood further reduced both albedo and the radiation reaching the soil, and adding multiple scattering within clumped layers significantly cut near-infrared albedo while boosting leaf absorption.

The team then compared modeled albedos against tower observations of reflected sunlight, the only component of the radiation budget routinely measured in the field. Both models overestimated broadband albedo by roughly 4 to 7 percent, but the modified Norman model came noticeably closer to the observations than its predecessor, thanks to stem absorption and the treatment of multiple scattering. The characteristic U-shaped diurnal pattern of albedo, higher when the sun sits low, was successfully reproduced. The residual overestimate could stem from uncertain optical properties of leaves, soil, or bark, which vary with moisture, or even from the metallic tower structure itself slightly biasing the measurements. The authors also note that the recollision probability theory was developed for needleleaf shoots, and its extension to broadleaf shoots, while supported by the results, deserves dedicated testing with models that represent every leaf as an explicit mesh.

The practical consequences ripple outward. Because stems absorb far more near-infrared than photosynthetically active radiation, including them will barely change carbon and latent heat fluxes, but it will strongly alter sensible heat fluxes and biomass heat storage, with implications for the persistent energy budget closure problem at flux towers. More dramatically, the simulations showed that omitting stems nearly doubles the radiation absorbed by the soil in both wavebands, a major distortion of the energy balance at the soil-air interface that may explain why land surface models have needed empirical corrections to under-canopy wind speeds. With the modified model, wood absorption is computed directly from canopy structure, resolved vertically, and free of ad-hoc partitioning, and the code and data are openly available on Zenodo for other modeling groups. Validation in needleleaf forests, savannas, and sparse canopies lies ahead, but for dense broadleaf forests, the trunks and branches that were once invisible to climate models can now finally be counted, and the forest’s hidden heat economy is coming into focus.

Subject of Research: Radiation absorption by woody stems in forest canopy microclimate modeling

Article Title: Consideration of radiation absorption by stems in forests for microclimate modeling

Article References: Béland, M., Bonan, G., Kobayashi, H., & Baldocchi, D. (2026). Consideration of radiation absorption by stems in forests for microclimate modeling. Geoscientific Model Development, 19(18), 9019-9033. https://doi.org/10.5194/gmd-19-9019-2026

Image Credits: AI Generated

DOI: 10.5194/gmd-19-9019-2026

Keywords: forest microclimate, radiative transfer, wood heat storage, ground lidar, canopy albedo, Norman model, near-infrared radiation, leaf clumping, eddy covariance, land surface modeling, 3D ray tracing, deciduous forests

The research, led by Grzegorz Fiutak of the University of Agriculture in Krakow together with Barbara Stefanska of the University of British Columbia and an international team spanning Poland and Canada, set out to answer a question that has long lingered at the margins of plant photobiology. Scientists know a great deal about how red, blue, and far-red light shape plant growth, because these wavelengths are absorbed by the pigments that drive photosynthesis and regulate development. But the near-infrared region beyond the far-red — roughly the band where 850 and 940 nanometer LEDs operate — has remained poorly understood. These wavelengths are widely used in consumer wellness devices and industrial heating applications, yet their direct effects on plant biochemistry, independent of photosynthesis, had not been systematically explored in an edible crop.

To probe the question, the team grew radish sprouts in complete darkness and compared them with sprouts cultivated under monochromatic near-infrared LEDs at 850 nanometers and 940 nanometers, with no visible light supplied at all. This design was critical: by excluding photosynthetically active radiation, the researchers could isolate any metabolic effects of near-infrared light from the familiar machinery of photosynthesis. They then subjected the harvested sprouts to an extensive battery of analyses, measuring dry matter, fiber, protein content, amino acid profiles, ascorbic acid, chlorophylls, carotenoids, anthocyanins, and phenolic compounds using high-performance liquid chromatography and other analytical techniques. Finally, they tested whether extracts from the sprouts had measurable biological activity in cell-based assays.

The results were striking in their wavelength specificity. Sprouts grown under 940 nanometer radiation accumulated the highest protein content of any treatment, while maintaining a stable amino acid profile and high protein quality — meaning the extra protein was not simply diluted in quality but retained a balanced composition of essential amino acids. This is a notable outcome for a crop grown entirely without visible light, and it suggests that deep near-infrared exposure may influence nitrogen metabolism or protein synthesis pathways through mechanisms that do not depend on photosynthetic energy capture. For controlled-environment agriculture, where protein enrichment of crops is an ongoing goal, the finding points to a potentially simple lever: changing the wavelength of supplementary lighting rather than altering inputs like fertilizer.

The 850 nanometer treatment told a very different story. Rather than boosting protein, this wavelength promoted the accumulation of ascorbic acid — vitamin C — along with anthocyanins, the pigments responsible for red and purple coloration in plants, and several carotenoids. The effect was visible to the naked eye: sprouts under 850 nanometer light developed more intense red pigmentation than their dark-grown counterparts. Anthocyanins are of intense interest to food scientists because of their antioxidant and anti-inflammatory properties, and carotenoids such as lutein are valued for their roles in eye health and as dietary antioxidants. The fact that a single, precisely chosen invisible wavelength could elevate these compounds without any photosynthetic input is the kind of result that lends itself to immediate application in vertical farming and sprout production facilities.

Importantly, the two treatments shared some common ground. Both 850 and 940 nanometer radiation increased the concentrations of lutein, violaxanthin, and selected derivatives of sinapic acid relative to sprouts grown in darkness. Sinapic acid derivatives belong to the broad family of phenolic compounds that plants deploy as chemical defenses and antioxidants. Their elevation under both wavelengths indicates that near-infrared exposure, even beyond the far-red region, acts as an elicitor of secondary metabolism — the branch of plant biochemistry responsible for producing many of the compounds humans prize in fruits, vegetables, and herbs. At the same time, some fundamentals proved stubbornly resistant to manipulation: dry matter, fiber content, and the overall amino acid composition of the sprouts remained unaffected by either treatment, and neither wavelength restored chlorophyll synthesis or prevented the etiolated growth pattern typical of plants raised in the dark.

Perhaps the most intriguing results came from the biological activity assays. The team extracted carotenoids from the sprouts using acetone-based methods and tested these extracts on Raw 264.7 macrophages, a widely used mouse cell line in immunology research. The cells were stimulated with lipopolysaccharide, a bacterial molecule that triggers a strong inflammatory response, and the researchers measured the production of interleukin-6, a pro-inflammatory signaling molecule implicated in chronic inflammatory diseases. The extracts from sprouts grown under 940 nanometer radiation were the most effective at reducing lipopolysaccharide-induced interleukin-6 production, outperforming extracts from the dark-grown and 850 nanometer treatments. While cell-culture findings are an early step and cannot be directly translated into health claims for consumers, they provide a proof of concept that light-grown sprouts can carry not just different nutrient profiles but measurably different bioactivity.

The broader significance of the study lies in what it says about light as a tool rather than merely as fuel. Photosynthesis is the process by which plants convert visible light into chemical energy, and most agricultural lighting strategies are built around maximizing it. But plants are also exquisitely sensitive photoreceivers in other ways, and this work demonstrates that near-infrared radiation beyond the far-red range modifies plant metabolism independently of photosynthesis altogether. In practical terms, this means growers could potentially use narrow-band near-infrared LEDs as elicitors — a kind of biochemical seasoning applied through the lighting system — to tailor crops for specific nutritional or functional goals. A producer targeting protein enrichment might favor 940 nanometer supplementation, while one aiming to maximize antioxidant content and visual appeal might choose 850 nanometers.

The implications extend to sustainability as well. Sprouts are among the most resource-efficient foods humans produce, requiring minimal water, space, and time from seed to harvest, and they are increasingly grown in controlled-environment facilities where every aspect of light, temperature, and humidity can be tuned. If a simple change in LED wavelength can elevate vitamin C, anthocyanins, carotenoids, or protein in such a crop without additional agricultural inputs, the energy cost of that intervention may be modest compared with the nutritional gain. The authors suggest that wavelength-specific near-infrared radiation could become a practical instrument in controlled-environment agriculture and sustainable functional food production, complementing the red and blue lighting that dominates indoor farms today.

There remain open questions, as with any early-stage finding. The study was conducted on a single crop species, radish, and the mechanisms by which 850 and 940 nanometer light exert their distinct effects on protein accumulation and secondary metabolism have not yet been fully mapped. Whether the same wavelength-specific responses hold for other sprouts, leafy greens, or fruiting crops is unknown, and the anti-inflammatory signal observed in macrophage cultures will need to be followed through further biological testing before any dietary relevance can be established. Still, the central message is clear and, for a field accustomed to thinking about light in terms of photosynthetically active radiation, genuinely surprising: there is useful information in the invisible part of the spectrum, and plants are listening. As indoor farming scales up around the world, the humble radish sprout — grown in the dark, bathed in light no one can see — may turn out to be an early glimpse of a new kind of precision agriculture, one where the recipe for a more nutritious vegetable is written in nanometers.

Subject of Research: Effects of near-infrared LED radiation on the biochemistry and biological activity of radish sprouts

Article Title: Biochemical composition and biological activity of radish sprouts grown in near-infrared radiation

Article References: Fiutak, G., Filipczak-Fiutak, M., Sady, M., Jarzębski, M., Mohammadi, X., Klein, G.-R., Relova-Clegg, E., Pratap-Singh, A., Świąder, K., Kapusta, I., Kołton, A., Tabaka, P., Grabacka, M., & Stefanska, B. (2026). Biochemical composition and biological activity of radish sprouts grown in near-infrared radiation. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10053-3

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10053-3

Keywords: near-infrared radiation, radish sprouts, carotenoids, anthocyanins, ascorbic acid, protein content, plant biochemistry, LED lighting, controlled-environment agriculture, functional foods, interleukin-6, photobiology